Closed circuit hydraulic compression device with stroke-consistent pump intake

ABSTRACT

An improved, compact and efficient arrangement of axial piston hydraulic pump and hydraulic cylinder into a single self-contained compression or actuating device. A combination of back-flow volume-acting pump pistons and a hollow main piston rod that serves as both a working fluid container and a head-creating organ is introduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 60/565,344, filed on Apr. 26, 2004, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

This invention primarily relates to a field of portable self-containedhydraulic tools for such applications as cutting rods, cables and like,crimping, perforating and otherwise deforming various stiff materials,as well as spreading and lifting heavy objects to relatively shortdistance. But far broader use of the present invention is available, forinstance, in compact and light-weighted actuating devices applyinglinear force to various working members. These include robotic arms,bulldozer blades and forklift claws, retractable supports (planechassis, for one), actuators that open and close valves and so on. Thepresent invention is being especially helpful in the situations whereeach working member incorporates independent, portable and autonomoushydraulic circuit and power source thus notably adding survivability tothe machine in the event of main hydraulic system breakdown. In fact, itprovides for elimination of the main system altogether, if necessary.

Conventional devices present various approaches to the creation ofself-contained hydraulic tools. The invention of U.S. Pat. No. 4,998,351to Hartmeister, Mar. 12, 1991 offers efficient way to solve the problem.But it features pressurized reservoir that is being located in its owndesignated portion of the tool's body, thus making the latter larger andheavier then the present invention permits.

The invention of U.S. Pat. No. 6,446,482 to Heskey, et al., Sep. 10,2002 as well as many other tools available on the market (Ridgid ProPress, for one) uses collapsible container that serves the same purpose.But such approach, while being cost-effective and requiring lessaccurate calculation on design stage, does necessitate serious means toprotect the soft material of which the container is made. Also, for thefact that collapsible container surrounds the tool's body, size factorremains not being adequately addressed.

The invention of JP02001179530A to Kawamata, Jul. 3, 2001 also featuresthe fluid container located at a distance from other parts of themechanism. Besides aforementioned disadvantages, all three inventionsutilize rather conventional way of pumping, where both suction andpressurized discharge of fluid by pump pistons do occur in front of thelatter. This causes greater length of passageways (and therefore greaterloss of energy due to fluid friction, plus design complexity) andoverall tool's size then the present invention affords.

SUMMARY OF THE INVENTION

The present invention relates to a closed circuit hydraulic compressiondevice that substantially obviates one or more of the disadvantages ofthe related art.

Additional features and advantages of the invention will be set forth inthe description that follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theadvantages of the invention will be realized and attained by thestructure particularly pointed out in the written description and claimshereof as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIG. 1 shows a conventional self-contained compression tool of U.S. Pat.No. 6,446,482 to Heskey, et al., Sep. 10, 2002.

FIG. 2 shows a plane view of longitudinal vertical cross-section of thedevice of the present invention.

FIG. 3 shows a plane view of longitudinal diagonal cross-section of thedevice of the present invention.

FIG. 4 shows a plane view of transverse cross-section of the device ofthe present invention.

FIG. 5 shows an isometric view of a back-flow volume acting groovedpiston of the device of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

The present invention, in a broad sense, is a substantial improvementover conventional methods of arranging an axial piston hydraulic pumpand a hydraulic cylinder into single closed circuit unit. In oneembodiment, it introduces the following elements:

-   -   (a) the entire volume of working fluid necessary for the        operation of the tool or implement is contained within main        cylinder's bore and rod,    -   (b) pump pistons displace working fluid from their cylinders        during forward stroke in the same direction as that of        suction, i. e., working fluid circulates from the volume in        front of the main piston (and within the rod) via pump pistons        into the volume behind the main piston in the same direction at        any given moment throughout the entire duty cycle.

A primary object of the present invention is to arrange all elementsnecessary for achieving above described results in a mostspace-efficient fashion, yet for no loss to any benefits conventionalpossesses.

This invention described herein can be used for:

1. Reducing overall size of the tool or other implement by utilizingvolumes not only in front of the main piston, but also within hollowpiston rod for working fluid storage, thus eliminating any remotelylocated fluid reservoirs.

2. Reducing length of fluid passageways by placing suction check valvesin front of pump pistons (adjacent to fluid stowage volume in front ofthe main piston within its cylinder bore) and pressurized dischargecheck valves behind pump pistons (adjacent to main piston's cylinderbore).

3. Reducing precision and material requirements, simplifying design andadding reliability to the tool or implement by having pump piston'slength-by-diameter ratio notably greater then it is in cases of mostconventional devices, for no sacrifice to the length of the tool orimplement.

The following designations are used in the figures:

-   -   6—housing    -   7—piston rod    -   8—elastomer seal    -   9—cylindrical chamber    -   10—cylinder piston    -   11—return spring    -   12—cylinder piston seal    -   13—end cap    -   14—locknut    -   15—compensator piston    -   16—spring guide    -   17—compensator spring    -   18—passageways    -   19—intake passageways    -   20—intake valves    -   21—cylinders    -   22—pump pistons    -   23—intake springs    -   24—pump seals    -   25—discharge passageways    -   26—discharge valves    -   27—trigger valve    -   28—valve return spring    -   29—retaining seal    -   30—lock seal    -   31—return passageway    -   32—relief passageway    -   33—relief valve    -   34—charging/bleeding nipples    -   35—pump drive axle    -   36—swash plate

A preferred embodiment of Closed circuit hydraulic compression devicewith stoke-consistent pump intake comprises cylindrically shaped housing6. Front end of it features a circumferential opening. This openingaccommodates a piston rod 7 and an elastomer seal 8 is provided forpreventing fluid leakage. Housing 6 further comprises cylindricalchamber 9, whereas a longitudinal axis of the chamber and of the housingare one and the same.

Cylinder piston 10 is located within chamber 9. It is being pressedagainst rear wall of the chamber by return spring 11. Cylinder pistonseal 12 is provided so that fluid can not escape from a rear portion ofchamber 9 to its front portion, thus defining volume 9 a (in front ofpiston 10) and volume 9 b (behind piston 10) within chamber 9. Pistonrod 7 is hollow. Its front end accommodates threaded end cap 13 that canbe turned clockwise and counterclockwise thus adjusting a length towhich it extends forward. Front portion of cap 13 has an opening.Position of end cap 13 is fixed by a locknut 14.

Volume compensator piston 15 is inserted into hollow piston rod 7.Piston 15 features a spring guide 16. Compensator spring 17 is locatedaround the guide between cap 13 and piston 15, and is being partiallysurrounded by them. Guide 16 can protrude through the opening of cap 13.

Passageways 18 are arranged within cylinder piston 10 so that internalspace of hollow rod 7 is openly connected to volume 9 a of chamber 9. Atthe front end of volume 9 a there are intake passageways 19, eachfeaturing intake valve 20. Passageways 19 further lead to (throughoutintake valves 20) pump cylinders 21, all of the above described is shownon FIG. 2. Cylinders 21 are arranged along the axis of housing 6 so thatthey are symmetrical with respect to it, as shown by FIG. 4. FIG. 2further shows back-flow volume acting grooved pump pistons 22 (alsoshown on FIG. 5), each inserted into its respective pump cylinder 21.Auxiliary intake springs 23 are placed in front of every pump piston 22.

Rear ends of cylinders 21 feature pump seals 24 to prevent fluid fromescaping into drive area of the pump. Cylinders 21 further comprise highpressure discharge passageways 25, each accommodating discharge valve26. Discharge passageways 25 are located so that their openings coincidewith reduced diameter portions of pump pistons 22 when the latter arebeing at the foremost position. Passageways 25 further lead to(throughout discharge valves 26) volume 9 b of chamber 9.

FIG. 3 shows another axial cross-section of housing 6. This viewdemonstrates a trigger valve 27 that incorporates valve return spring28, fluid retaining seal 29 and trigger valve lock seal 30. Fluid returnpassageway 31 is arranged between volume 9 a and volume 9 b of chamber9. It is located in bottom segment of housing 6 between and along twolower pump pistons 22 and (also see FIG. 4). Trigger valve 27 protrudesthrough outer wall of housing 6 so that provisions for depressing andreleasing of the former can be added without interference with theinternal structure of the device.

FIG. 3 further shows relief passageway 32 and relief valve 33. These arealso arranged between volumes 9 a and 9 b similarly to fluid returnpassageway 31. Relief passageway 32 is shown in the top segment ofhousing 6, between and along two upper pump pistons 22. Fluid chargingand bleeding nipples 34 (two required, one shown) are located betweenvolume 9 a and the ambient media, shown in “tightened” position. Pleasenote that terms “bottom”, “top”, “upper” and “lower” are only relevantfor the purpose of these drawings and do not necessarily imply theirmeaning to the actual device of the present invention.

The preferred embodiment also comprises pump drive mechanism and rotarymotion source that fall beyond the scope of the present invention.However, for better illustration FIGS. 2 and 3 show pump drive axle 35and fixed angle swash plate 36, against which rear ends of pump pistons22 are pressed by springs 23. Just as well, varieties of workingattachments (that can be used with the device while being demountablyconnected to its front end) are not shown.

Operation of the Preferred Embodiment

When the device of the present invention is not charged with hydraulicfluid, or is not primed, compensator spring 17 keeps volume compensatorpiston 15 bias against the body of cylinder piston 10, similarly to theposition shown on FIG. 3. Cylinder piston 10 itself, however, is at thispoint pressed against the rear wall of volume 9 b of chamber 9, as shownon FIG. 2. Piston rod 7 is being therefore fully retracted into housing6. Priming and bleeding (or eliminating air from hydraulic fluid) willbe discussed at the end of this description.

FIG. 2 shows the device of the present invention in “ready to operate”position. Compensator spring is compressed by the fluid present in theentire system and, particularly, in front of volume compensator piston15 within hollow piston rod 7. When an operator depresses the triggerabout half-way, valve 27 closes return passageway 31 thus separatingvolumes 9 a and 9 b. When trigger is depressed all the way, rotarymotion source activates swash plate 36 and pump pistons 22 beginreciprocating within their cylinders.

At least one of pump pistons 22 makes forward (pumping) movement at anygiven moment when swash plate rotates. During such movement fluid incorresponding pump cylinder 21 is being displaced by invading volume ofpump piston 22. Resulting pressure acts to keep intake valve 20 closedwhile forcing discharge valve 26 to open. Fluid in front of pump piston22 by-passes back via grooves and proceeds through discharge passageways25 into volume 9 b of chamber 9, urging cylinder piston 10 to moveforward against resistance of a work load and/or return spring 11.

At least one of pump pistons 22 makes backward (intake) movement at anygiven moment when swash plate rotates. Cylinder piston's 10 forwardmovement causes fluid in volume 9 a of chamber 9 to flow throughcorresponding intake passageway 19 into its respective pump cylinder 21.At the same time volume compensator piston 15 is moved within piston rod7 towards cylinder piston 10 by compensator spring 17, urging fluid infront of piston 15 to flow through passageways 18 into volume 9 a ofchamber 9 and thus compensating a negative difference between volumes 9a and 9 b.

FIG. 3 shows the device of the present invention at the end of itsuseful work cycle. Cylinder piston 10 is pressed by fluid against fullycompressed return spring 11 and reduced diameter area of chamber 9 a.Compensator piston 15 has traveled all its way towards cylinder piston10, compensator spring 17 is only slightly compressed. Assuming theoperator still holds the trigger fully squeezed, trigger valve 27 isclosed and rotation of swash plate 36 continues, hydraulic circuit isbeing active through relief valve 33 opened by fluid pressure. Reliefpassageway 32 returns fluid from volume 9 b to volume 9 a, and thedevice is idling under high pressure.

If operator partially releases trigger, rotation stops, but triggervalve is still closed, so piston rod 7 remains fully extended. When theoperator lets go of the trigger, valve 27 opens, fluid under pressurecreated by return spring 11 escapes from volume 9 b back to volume 9 aand into hollow piston rod 7, forcing compensator piston 15 to movetowards end cap 13 and to compress compensator spring 17.

In order to charge the device of the present invention with fluid andbleed air from its hydraulic system, there is no need for any separatepriming pump. Two flexible hoses must be placed over heads of partiallyunscrewed charging and bleeding nipples 34. Opposite ends of these hosesmust then be placed into a jar full of fluid of choice. One of thesehoses has a foot valve, another has one-way check valve so that flow inboth hoses throughout volume 9 a can occur in one direction only. Oncehoses are submerged into fluid in the jar, operator depresses thetrigger and holds it for awhile.

At this point auxiliary intake springs 23 play their role. They keeppump pistons 22 in contact with swash plate at any time so that suctioneffort materializes upon rearward movement of pistons. Fluid thereforeenters volume 9 a through the hose with foot valve and starts fillingthe system, thereby urging the air to escape through the hose with checkvalve. This shortly causes pressure buildup within volume 9 b andcylinder piston 10 starts moving forward. Once that occurs, operatorrepeatedly releases and depresses the trigger until piston rod 7 extendsfully forward (to the point of opening of the relief valve 33) andreturns fully back, driving the remaining air out of the system.

When no more air bubbles are observed escaping the system, operatorpartially releases the trigger as soon as piston rod reaches full extentforward. Without letting the trigger go operator then immediatelytightens the nipple with check valve hose. Then he/she releases thetrigger completely, trigger valve opens and fluid from volume 9 b isdriven into volume 9 a and hollow piston rod 7 by return spring 11,forcing compensator piston 15 to compress compensator spring 17. Thisprocedure must be repeated two-three times. Upon doing so, some more airbubbles will show escaping. When it happens no longer, both nipples mustbe tightened, hoses removed and stowed, the device of the presentinvention is charged and ready to operate.

Alternative Embodiments

The closed circuit hydraulic compression device with stroke-consistentpump intake of the present invention is primarily intended to be used asa core element of hand-held tools for cutting, crimping, deforming andperforating of various objects made of metals and other stiff materials.However, it can also be utilized as part of any stationary equipmentwhere compression force is required and compact design is being a matterof importance.

Housing 6 may be of prismatic or other suitable shape. Axis of thehousing and of cylinder piston do not necessarily have to coincide or tobe precisely parallel.

A highly desirable alternative embodiment presumes a replacement ofcompensator piston 15 and spring 17 by a collapsible elastomercompensating container. Such design change eliminates a necessity ofprecision machining of hollow piston rod's 15 bore. Passageways 18 canthen be arranged through walls of hollow piston rod 7 instead of thebody of cylinder piston 10. Also, the opening to ambient media in endcap 13 can be done away with in order to nullify sensitivity of thedevice to a pressure and chemical aggressiveness of the media. Finally,both return passageway 31 and relief passageway 32 can be locatedwherever it is convenient and functional, including their unification bya slight change of trigger valve's 27 design or routing them throughpump drive area.

It will be understood by those skilled in the art that various changesin form and details may be made therein without departing from thespirit and scope of the invention as defined in the appended claims.Thus, the breadth and scope of the present invention should not belimited by any of the above-described exemplary embodiments, but shouldbe defined only in accordance with the following claims and theirequivalents.

1. A closed circuit hydraulic compression device comprising: a housing;a main hydraulic cylinder within the housing and comprising a hollowrod, a main piston, a bore, a piston seal, means for returning the mainpiston to a predetermined position within the bore after commencing astroke to any distance, and means for preventing a loss of a workingfluid, wherein the hollow rod includes means for containing the workingfluid under a predetermined pressure, wherein the main piston allows afree passage of the working fluid in both directions between a spacewithin the hollow rod and a space within the bore in front of the mainpiston, wherein the bore in front of the main piston permits anunobstructed outward flow of the working fluid from the space within thebore in front of the main piston while preventing a reverse flow; agroup of pump cylinders located within the housing and orientedapproximately parallel to a longitudinal axis of the main cylinder,wherein a front portion of each pump cylinder is openly connected to themeans of preventing the reverse flow of the working fluid into the spacewithin the bore of the main cylinder in front of the main piston and arear portion of each cylinder has means to allow unobstructed flow ofworking fluid into a space within the bore behind the main piston whilepreventing the reverse flow, wherein the means to allow for unobstructedunidirectional flow of working fluid from the bore in front of the mainpiston via the pump cylinders into the bore behind the main pistonremain functional throughout a full predetermined stroke of the mainpiston, each pump cylinder further incorporating a pump piston and afluid-tight seal between a rear portion of the pump piston and a rearportion of the pump cylinder, wherein the rear portion of each pumppiston extends beyond the fluid-tight seal so that a predeterminedreciprocal movement of the pump piston is allowed, each pump cylinderfurther incorporating means to return pump piston to a predeterminedposition after commencing a stroke to any distance, each pump pistonfurther comprising means to allow for unobstructed flow of the workingfluid in a direction approximately parallel to a longitudinal axis ofthe pump piston, means to allow for a return of the working fluid fromthe bore behind the main piston into the bore in front of the mainpiston throughout a duty cycle of the closed circuit hydrauliccompression device; means to impart reciprocal movement to the pumppistons; and means to allow for charging the closed circuit compressiondevice with the working fluid and for subsequent elimination of gasbubbles from the working fluid.
 2. The closed circuit hydrauliccompression device of claim 1, further comprising manual means tocontrol means to allow for the return of the working fluid.
 3. Theclosed circuit hydraulic compression device of claim 1, furthercomprising automatic means to control means to allow for the return ofthe working fluid.
 4. The closed circuit hydraulic compression device ofclaim 1, further comprising means to prevent an increase in pressure ofthe working fluid above a predetermined value.